The term "enterochromaffin cell" was introduced more than 100 years ago. The cells that are morphologically similar to the enterochromaffin cells have been referred to as "enterochromaffin-like cells". One of the enterochromaffin-like cell populations in the oxyntic mucosa of stomach is known to produce and store histamine and chromogranin A, and referred to as ECL cells. The biology and the functional morphology and topology of the ECL cells have been extensively studied, since they were discovered 45 years ago. ECLcell histamine plays an important role in the regulation of gastric acid secretion, particularly in response to gastrin stimulation. The timecourse responses of ECL cells to gastrin include mobilization of histamine, hypertrophy, hyperplasia, dysplasia and formation of ECLcell carcinoids. The ECL cells are controlled by a complex regulatory system involving endocrine, paracrine and neural pathways. The physiological significance of ECL cells reflects the nature of their products such as histamine, chromogranin A-derived peptides, Reg protein and yet-unknown hormone.